one of them, after all, has been president for four years. the other has been running for longer than that. barack obama and mitt romney are both nearing the end of intense debate prep, and coaching sessions. and at this point, they're designed either to create or prevent that moment that we've all seen that can somehow change the race. and with millions of americans watching these debates like a kind of super bowl of american politics, the stakes are high as the two men face each other in denver, just two days from now. we begin tonight with nbc's andrea mitchell in our d.c. newsroom. andrea, good evening. >> good evening, brian. it is the political super bowl, or perhaps the world series. mitt romney, behind in all battleground polls for the last three weeks, now has the most to gain from a game-changing night. and the most to lose if he doesn't turn it around. as the candidates head to debate camp, rolling up their sleeves, getting down to work, each claims to be the underdog. >> governor romney, he's -- he's a good debater.